Electrical components often contain molded parts that are formed from a liquid crystalline, thermoplastic resin. Recent demands on the electronic industry have dictated a decreased size of such components to achieve the desired performance and space savings. Unfortunately, however, it is often difficult to adequately fill a mold cavity of a small dimension with most conventional liquid crystalline polymers. For instance, conventional formulations are generally derived from aromatic hydroxy acid monomers (e.g., hydroxybenzoic acid (“HBA”) or 6-hydroxy-2-naphthoic acid (“HNA”)), either alone or in conjunction with other aromatic monomers, such as diacids (e.g., terephthalic acid (“TA”) or isophthalic acid (“IA”)) and/or diols (e.g., hydroquinone (“HQ”), acetaminophen (“APAP”), and 4,4′-biphenol (“BP”)). Unfortunately, such polymers tend to display a very high solid-to-liquid transition temperature (“melting temperature”), which precludes their ability to flow well at temperatures below the decomposition temperature.
To suppress the melting point and generate materials that can flow, additional monomers are often incorporated into the polymer backbone as a repeating unit. One commonly employed melting point suppressant is naphthalene-2,6-dicarboxylic acid (“NDA”), which is generally believed to disrupt the linear nature of the polymer backbone and thereby reduce the melting temperature. The melting point of a wholly aromatic liquid crystal polyester may be lowered by substituting NDA for a portion of the terephthalic acid in a polyester of terephthalic acid, hydroquinone and p-hydroxybenzoic acid. In addition to NDA, other naphthenic acids have also been employed as a melt point suppressant. For instance, 6-hydroxy-2-naphthoic acid (“HNA”) has been employed as a melting point suppressant for a polyester formed from an aromatic diol and an aromatic dicarboxylic acid. Despite the benefits achieved, the aforementioned polymers still have various drawbacks. For example, the reactivity of the naphthenic acids with other monomeric constituents can have unintended consequences on the final mechanical and thermal properties of the polymer composition. This is particularly problematic for molded parts having a small dimensional tolerance. In addition to functional concerns, the high cost of naphthenic acids also dictates that the need for others solutions to the problems noted.
As such, a need exists for a low naphthenic, liquid crystalline thermoplastic composition that can readily fill mold cavities of a small dimension, and yet still attain good mechanical properties.